1. Field of the Invention
This invention relates to wireless sensing systems. More specifically, the invention is a wireless sensing system for non-invasive monitoring of attributes of a non-gaseous material in an electrically non-conductive container (e.g., level, temperature, change to contents' magnetic permeability, dielectric constant and other measurable property attributes. A further embodiment of the present invention monitors the attributes of a non-gaseous material in an electrically conductive container.
2. Description of the Related Art
Fluid level and/or other attributes (e.g., temperature, magnetic permeability, dielectric constant) of a fluid in a container are typically monitored by a device positioned or installed in the container. For example, a container's fluid level could be monitored manually using a conventional dipstick that is inserted into the container and then removed with the fluid level being indicated on the dipstick. A variety of “in container” fluid level measurement systems using floats, capacitive probes and fiber optics are also well known in the art.
More recently, a wireless fluid level measuring system was disclosed in U.S. Pat. No. 7,255,004. Briefly, this system includes a level-sensing probe positioned in a tank. The probe is divided into sections, with each section including (i) a fluid-level capacitive sensor disposed along the length thereof, (ii) an inductor electrically coupled to the capacitive sensor, (iii) an external antenna positioned for inductive coupling to the inductor, and (iv) an electrical conductor coupled to the external antenna. An electrically non-conductive housing accessible from a position outside of the tank houses inductors arrayed in a pattern. A magnetic field response recorder has a measurement head with transceiving antennas arrayed therein to correspond to the pattern of the housing's inductors. When a measurement is to be taken, the measurement head is mechanically coupled to the housing so that each housing inductor is substantially aligned with a specific one of the transceiving antennas.
While the various manual and automatic fluid level measurement systems generally perform well, it is not always possible or prudent to position/install a fluid level measurement or other fluid attribute monitoring system in a container.